Telephone system



July 8, 1941. A. J, BUSCH 2,248,566

. TELEPHONE SYSTEM Filed Apr il 19, 1939 14 Sheets-Sheet 1 g I IHI- L]:

@ lNl/ENTOR B AJBUSCH ATTORNEY July 8, 1941. A. J. BuscH TELEPHONESYSTEM 14 Shets-Sheet 2 Filed April 19, 1959 July 8, 194 1.

A. .1. BUSCH TELEPHONE SYSTEM l4 Sheets-Sheet 3 Filed April 19, 1959 NOWR H U J M w. N R m T A July 8, 1941. A, J, BU CH 2,248,566

TELEPHONE SYSTEM Filed April 19, 1939 14 Sheets-Sheet 4 L W il ATTORNEYJuly 8, 1941. A. J. BuscH TELEPHONE SYSTEM 14 Sheets-Sheet 5 Filed April19, 1939 IN VE N TOP A. J. BUSCl-l A TTORNE V July 8, 1941. BUSCH2,248,566

TELEPHONE SYSTEM Filed April 19, 1939 l4 Sheets-Sheet 6 IN [/5 N TOR aamA 7' TORNE V July 8, 1941. BU H 2,248,566

TELEPHONE SYSTEM Filed April 19, 1939 14 Sheets-Sheet v //v VENT 4. J.BUSCl-l 51 ATTORNEY July 8, 1941. A. J. BUSCH TELEPHONE SYSTEM FiledApril 19, 1939 14 Sheets-Sheet 8 lA/l/E'NTOI? By A.J.BUSC/-/ 6913 M.5316 L 6528 1:96 mn ISSUE-U A JOEFZOU UH? \Nk WNK kNk ATTORNEY y 1941-A. J. BuscH 2,248,566 TELEPHONE SYSTEM Filed April 19, 1939 14Sheets-Sheet 9 51L con-ram. cmcurr z" CONTROL cmcurr A T TORNE V July 8,1941. A. J. BUSCH TELEPHQNESYSTEM Filed April 19, 1939 .14 Sheets-Sheet1O lNVENTO/Q A. J. BUSCH ATTORNEY July 8, 1941. sc 2,248,566

TELEPHONE SYSTEM Filed April 19,1939 14 Sheets-Sheet 11 INI/ A.J.BU$CH rATTORNEY 14 Sheets- Sheet 12 Filed April 19, 1959 SNx 23 INVENTOR A J.BUSC H A TTORNEV Jul 's, 1941. J, BUSCH. 2,248,566

TELEPHONE SYSTEM Filed April 19, 1939 l4 Sheets-Sheet l3 INVENTOR A J.BUSCH A TTORNE V July 8, 1941.

FIG. /4

A. J. BUSCH TELEPHONE SYSTEM Filed April 19, 1959 14 Sheets-Sheet 14 /Nl EN 70/? y AJ. BUSCH ATTORNEY Patented July 8, 1941 NT FFICE 'rELErnoNnSYSTEM Application April 19, 1939, Serial No. 268,651

12 Claims.

This invention relates to telephone systems and more particularly tosystems in which automatic switching equipment is employed forestablishing connections.

- It has been the practice heretofore in automatic telephone systems toprovide a plurality of coin-control mechanisms at the central ofiicecommon to the coin district trunks in the centralomce, any one of whichmay be seized over an idle link circuit by a trunk having a call thereonestablished from a coin box substation, fora brief interval near the endof each period of conversation and an idle one of which may be seizedfor a brief interval at the end of each such period. When the controlmechanism isv connected to a trunk near the end of a conversationalperiod, it proceeds to collect the coin that was previously deposited atthe calling substation in payment for the conversational period. At thistime the control mechanism also transmits a warning tone to the callingsubscriber advising him that the conversational period is about toexpire and that he should deposit an additional coin if he wishes tocontinue the conversation. On its subsequent connection to the trunk,namely, at the end of the full conversational period, the controlmechanism makes a test to determine whether the calling subscriber hasdeposited an additional coin for the next conversational period. If themechanism fails to find a deposited coin when it attempts to collect onits first association with the trunk near the end of the conversationalperiod, a monitoring operator is signaled and she makes connection withthe calling line by way of a jack which is individual to the controlmechanism and challenges the calling subscriber requesting him todeposita'coin. When he does so she immediately collects the coin and withdrawsfrom the connection. If the coin-control mechanism fails to find a coinwhen it tests the line at the end of any conversational period, itsignals the monitoring operator and she makes connection with thecalling line and requests the calling subscriber to deposit the coin inpayment for the next conversational period. When the subscriber depositsan additional coin or advises the operator that he has already done so,she withdraws from the connection.

The control mechanism is also arranged to make a retest of the callingline for the presence of a coin after the monitoring operator withdrawsfrom the connection following her request that the calling subscriberdeposit an additional coin for the next conversational period. If on theretest the control mechanism finds that a coin has been deposited, themechanism is disconnected and returns to common use, but, if the retestshows that no coin is present in the coin box, the mechanism againsignals the monitoring operator and she returns to the connection andrequests the calling subscriber to deposit a coin. On each withdrawal ofthe monitoring operator, the control mechanism tests the line for thepresence of the coin and will not retire from the connection until thetest has been satisfied.

Since the monitoring operator obtains connection to any calling coinline by Way of jacks which are individual to the common controlmechanism rather than by way of connecting circuits individual to thecentral office trunks, the operators positionsare concentrated.

The object of the present invention is to improve the service renderedby circuits of the character disclosed in the event that peak loadconditions occur.

A feature of the present invention is the provision of a coin-controlrelease circuit common to a plurality of coin-control mechanisms whichfunctions to release all coin overtime calls which have been unansweredby a monitoring operator and tocancel the test for the presence ofdeposited coins on coin collect calls when all coincontrol mechanismshave become busy due to a peak load condition, whereby coin-controlmechanisms will be made available for use for regular coin collect andcoin return service.

A further feature is the provision whereby an alarm and a visible signalare operated when a coin district trunk is excessively delayed due tothe fact that no link circuit is available for connecting such trunk toa coin-control mechanism to identify the delayed group of coin districttrunks to a maintenance man.

These and other features of the invention will be described more fullyin detail in the following description and will be set forth in theappended claims.

Referring to the drawings which accompany the detailed description:

Fig. 1 shows a district junctor circuit arranged to function with acoin-control circuit and connected conventionally with a coin boxsubscribers station by a line link and group control circuit consistingessentially of cross-bar switches;

Fig. 2 shows in abbreviated schematic form the connection of thedistrict junctor of Fig. 1 to a district link frame and thence throughan ofiice link frame to an outgoing trunk;

Fig. 3 shows in abbreviated form the termination of the trunk of Fig. 2and its connection through the cross-bar switches of incoming link andline-link circuits to a called subscribers line;

Fig. 4 illustrates in abbreviated manner, the connection of the districtjunctor of Fig. 1 through a subscriber link and control circuit to asubscriber sender conventionally represented by a box;

Figs. 5, 6, '7 and 8 placed with Fig. 6 above Fig. 5, Fig. 7 to theright of Fig. 6 and Fig. 8 beneath Fig. 7, illustrate a link and controlcircuit whereby a connection between the district junctor circuit ofFig. 1 and the coin-control circuit of Figs. 9 to 12, inclusive, may beestablished, portions of other links and control circuits beingdisclosed in Fig. 8;

Figs. 9, 10, 11 and 12 placed with Fig. 10 beneath Fig. 9, Fig. 11 tothe right of Fig. 9 and Fig. 12 beneath Fig. 11, illustrate acoin-control circuit, other coin-control circuits being schematicallyindicated by the boxes in Fig. 9;

Fig. 13 illustrates a coin-control release circuit in accordance withthe present invention, common to a plurality of coin-control circuits;

Fig. 14 shows a link busy alarm circuit; and,

Fig. 15 is a diagram showing the manner in which the several figures ofthe drawings should be arranged to show the complete circuit.

General description The invention is illustrated in an automatictelephone system in which automatic switches of the cross-bar type areused as a medium for extending connections from subscribers lines overtrunks to other subscribers lines. These cross-bar switching mechanismsare controlled by register senders at the central office which receivethe designations of wanted lines from the calling subscribers dial andby decoder markers which are connectable to the sender for receivinginformation from the sender and which are connectable to the properswitch frame for the purpose of testing the outgoing trunk, for testingthe connecting link and for operating the magnets of the cross-barswitches to establish the connection.

While the system disclosed is not limited to the use of cross-barswitches of any particular type, reference may be had to the patent toReynolds 2,021,329, of November 19, 1935, for an understanding of theconstruction and operation of a switch suitable for use in such systems.Because of the complicated nature of these systems and since it is notnecessary for an understanding of the invention that the system in allof its details be disclosed, much of the circuits and equipment has beeneliminated in the present disclosure for the sake of simplicity and inthe following description reference will be made to numerous operationswhich are not fully disclosed in all their details. Whenever suchreferences occur it will be understood that the circuits and equipmentso referred to are already known and in particular are disclosed andcompletely described in Carpenter Patent 2,093,117, granted September14, 1937, and Carpenter application Serial No. 214,356, filed June 17,1938.

The subscribers lines, such as line I00, are connected to verticals ofthe primary crossbar switches indicated conventionally by the apparatusof box l0! and thence extended through secondary switches such as switchI02 to district junctor circuits. The connections to the districtjunctor circuit are efiected by means of a line link and group controlcircuit and a subscriber sender link and control circuit. The circuitdetails (not shown) whereby these connections to the district junctorcircuit are effected may be the same as in Carpenter Patent 2,093,117and in Carpenter application Serial No. 214,356, above mentioned.

When the connection to the district junctor, which is one of a group ofsimilar junctors (not shown) is established as above outlined, thesubscriber sender 400 through a link circuit represented schematicallyby primary and secondary cross-bar switches 40| and 402, functions inconnection with a marker circuit indicated by the box 200 to establish aconnection to an outgoing trunk 206 in accordance with the office codedialed at the sailing station I03 and recorded by the sender 400. Thisconnection is established through district frame cross-bar switches 20!and 202 and oflice frame switches 203 and 204.

When the outgoing trunk 206 is thus seized, a connection is establishedthrough an incoming link and connector circuit consisting of cross-barswitches 300 and 30l and line-link circuit consisting of cross-barswitches 302 and 303 to the line of the called subscriber 304. After thesubscriber of station 304 answers, this condition is registered in thedistrict junctor of Fig. 1.

The district junctor of Fig. 1 has common access to a group ofcoin-control circuits one of which is shown in Figs. 9 to 12, inclusive.The connection to a selected coin-control circuit is made by means ofthe link and control circuit of Figs. 5 to 8, inclusive, which consistsessentially of primary and secondary cross-bar switches 10! and 102.

The district junctor circuit of Fig. 1 is arranged to summon thecoin-control circuit of Figs. 9 to 12, inclusive when required asfollows:

(a) To collect a coin after a completed connection immediately after thecalling subscriber has disconnected;

(b) To collect a coin during conversation at the end of a predeterminedinterval;

(0) To return a coin after an incompleted connection immediately afterthe calling subscriber disconnects or on a free call;

(d) To test for the presence of an additional coin at the beginning ofan overtime period and in case no coin is found to summon an operatorfor overtime monitoring on the connection.

In the case of condition (a) the coin-control circuit makes a test todetermine the presence or non-presence of a coin in the coin box I04 andto determine whether or not the coin box N34 has been properly clearedafter the application of coin collect current. For either of theseconditions lamp H00 is flashed to inform an operator of the failure tocollect the coin. For condition (12) should the coin-control circuitfail to find the coin, lamp I IN is immediately flashed to inform theoperator of this condition. For condition (c) lamp H00 is lightedsteadily if the coin box is not properlycleared after the application ofcoin return current. For condition (d) the operator is summoned by thesteady lighting of lamp I l0l if the test indicates that no coin ispresent.

In the event of a peak load causing all coincontrol circuits to becomebusy thereby indicating that no coin-control circuit is then availablefor the use of another district junctor, a chain circuit is closed overcontacts of relays 800, etc., individual to the link control cir cuitsto start the coin-control release circuit of Fig. 13 which is firsteffective to operate a multicontact relay, such as i300, to close loopcircuits to all of the coin-control circuits and to operate otherrnulticontact relays, such as I30I, to ground other conductors extendingto coincontrol circuits. The rel-ease circuit then proceeds to measure atime interval of 60 to 90' seconds. If during this time interval any oneof the coin-control circuits has been seized on an overtime call, andits overtime relay I000 is thus operated, it will be immediatelyreleased provided the coin-control circuit is still awaiting theresponse of a monitoring operator. It is assumed that at the expirationof this time interval, the peak load condition of all coincontrolcircuits being busy .will have passed or be sufficiently relieved sothat upon the release of the multicontact relay I300, the coin-controlcircuit may again serve coin overtime traffic.

Following the measurement of this time interval, a further interval of 6to 8 minutes is measured, during which the multicontact relays 533! aremaintained operated. During this interval the operation of thecoin-collect relay IOI of any coin-control circuit will cause theoperation of the no-coin test relay I002 of such coincontrol circuit onall coin collect calls to cancel the test for a deposited coin wherebythe coincontroi circuit will be released immediately following theapplication of coin collect current without Waiting to test for thepresence of a coin or to signal the operator in the event no coin hasbeen deposited. If at any time during the latter interval, a peak loadcondition again occurs and all coin-control circuits become busy, thecoin-control release circuit is arranged to start another coin-controlrelease interval.

Detaiied description of operation The operation of the system will nowbe described in detail and for this purpose let it be assumed that thecalling subscriber of station 03 initiates a call by depositing a coin Iin the coin box set and by removing the receiver from the switchhook ofthe substation equipment of station W3. A circuit is thereby closed' foroperating relay I56 which c'ircuit may be traced from, battery throughthe winding of relay I06, lowermost contact of cross-bar switch holdmagnet 58?, over the ring conductor of line I00 through the switchhookcontacts of station 103 and the winding and associated contacts H58 ofcoin collect magnet IE8 to ground at I09. Line relay I08 functions incooperation with the line link and group control circuit of Fig. 1, thesubscriber sender link and control circuit and subscriber sendercircuits of Fig. 4 to effect the selection of an idle district junctcrcircuit, of an idle line link extending thereto and of the circuitclosure of said link. The idle condition of the district ,iunctorcircuit is indicated by the presence'of battery on busy test conductorH3. The circuit details whereby this is accomplished are shown in theaforementioned application of W. W. Carpenter Serial No. 214,356, filedJune 1?, 1938.

The selection before stated having been made, cross-bar switch contactsof the primary switch Ii)! and of the secondary switch I02 are closedextending the conductors of line I00 to conductors I it] and Iii whichterminate respectively on the upper outermost and lower innermost backcontacts of relay H2 through which contacts connection is made overconductors I I4 and -II5, through the cross-bar switch contacts of thesender link and control circuit represented diagrammatically by boxes40I and 402, to subscriber sender 400. Dial tone is now furnished overthese conductors as an indication to the subscriber at station I03 thatdialing may be started. Ground is also connected at this time by thehold magnet 404 of the sender link and control circuit to conductor IIBwhereby relay III is operated over a circuit which may be traced frombattery through the winding of relay II'I, next to upper innermost backcontact of relay NZ to ground on conductor H6. Relay I l! upon operatingperforms no useful function at this time except to disconnect busy testbattery H8. from test conductor H3, this circuit being traced frombattery I I8 through resistance H9, upper outer back contacts of relaysI20 and I2I, lower back contact of relay II'I, lower back contact ofrelay I2l, inner lower back contact of relay ,I'I2,,upper back contactof relay I36 to conductor II 3. This disconnection of battery H8 makesthe district junctor test busy to the sender link and control circuit onsubsequent calls. Hold magnet 03 of the sender link and control circuitalso connects ground to conductor I22 which is extended through theupper outer back contact of relay I23 through resistance I24 to sleeveconductor H25 thereby supplying holding ground for the line-link holdmagnets I 01 and I26 while the sender 400 is connected to the districtjunctor circuit.

While the connection is being established from the calling line I00 tothe sender circuit 400, the subscribers sender link and control circuitof Fig. 4 is momentarily connected to sender circuit 400 and during thisinterval, sender circuit 400 is furnished with the class of serviceinformation of line E00 and is also informed of the number of thedistrict link and connector frames associated with the district junctorcircuit to which the sender 400 is connected. The line link and groupcontrol circuit and the subscriber sender link and control circuit areused only momentarily to connect line I 00 to an idle district junctorcircuit and to a subscriber sender circuit and are then released toserve other calls but the connections through the cross-bar switchesIOI, I02, 40I and 402 which these circuits have established are held bythe sender circuit 400 under the control of the calling subscriber.After the ofiice code has been dialed, sender 4G0 connects to theoriginating marker 200 by means of a connector circuit 405 over a groupof conductors represented by the broken line 400. The sender circuit-400registers in the marker circuit 280, the office code, the class ofservice information of the calling line I00 and the number of thedistrict link and connector frame serving the district junctor circuitinvolved in the call, The marker 200 then furnishes the sender 490 withthe necessary information which it requires to control the progress ofthe call. Marker 250 then selects an ofiice link and connector frame onwhich the desired trunk 206 leading to the called destination appears,connects itself thereto and also to the district link and connectorframe that is associated with the district junctor circuit involved inthe call. After this has been successfully done marker 200 connectsground to a conductor which is extended through connector 405, sender400 and the sender link circuit consisting of switches MI and 402 toconductor I13, thereby operating district junctor relay I 21. Relay I21upon operating connects ground over its upper middle contact toconductor I28 thereby operating select magnet 205 of the primary switchZUI of the district link and connector frame serving the districtjunctor of Fig. 1 and connects ground over its inner lower contact toconductor I3I thereby operating relay 201 which is common to a group ofdistrict junctors served by the primary switch represented by box I. Theoperation of relay 201 extends conductors I29, I30, I3I, I32 and 209through contacts of a marker connector relay to the marker circuit 200selected for handling the call being established. This connector relay(not shown) being indicated only by the broken lines is individual tothe marker circuit 200 and is operated each time that marker 200 isselected for service in establishing a connection to the district framerepresented by Fig. 2. Conductor I29 is used by marker 200 to determinewhen the primary switch 20I has operated, from ground supplied by themarker over conductor 209. This is effected by the extension of theaforesaid ground through the lowermost primary switch contact associatedwith magnet 208 over conductor I14 through the uppermost front contactof relay I21 over conductor IE9 through the next to upper contact ofrelay and a contact of the aforesaid marker connector relay (not shown)to marker 200. Conductor I30 is grounded by marker 200 and is extendedthrough the next to inner upper contact of relay 201 and the upperinnermost front contact of relay I21 to operate relay I33 for calls toan operator. Conductor I3I is used by the marker 230 to hold relay I21operated through its lower innermost contact until the marker 200releases as hereinafter described and conductor I32 is extended over theinner upper contact of relay 201 and through the lower contacts of relayI21 and conductor I to give the sender 400 a trouble release signal if atrouble condition has been encountered by marker 200 in establishing theconnection. If the relay I33 is operated, it will lock through its lowerinner contact to ground supplied by the sender 400 over conductor I34.

Marker 200 now establishes the connection through the district andoffice switches to trunk 206. Select magnet 2"] of secondary districtswitch 202 is operated by ground on the lower contacts of relay 201.Select magnet 2I2 of the primary office switch 203 is operated by groundon the upper contact of relay 2 I3 and select magnet 2I4 of thesecondary switch 204 by ground on the contacts of relay 2 I5, both ofwhich relays are operated by marker 200.

is established when relay 2I9 is operated by The link between V thesecondary district and primary office switches marker 200 and operateshold magnets 2H and 2I1 from ground over conductor 2I6. The link betweenthe primary and secondary switches of the office frame is completed whenhold magnet 2I8 is operated from ground in the marker over the lowercontacts of relay 2I3.

After the marker 200 has established connection with the trunk 206 asbefore described, it releases relay I21 by removing ground from thewinding of relay 201. Relay I21 releases and closes the sleeve conductorI14 to the ground on the inner upper front contact of relay I I1. Marker200 tests for this ground and if it finds it, disconnects. Relay I I1was operated over conductor I10 when the sender link and control circuitconnected sender 400 to the district junctor of Fig. 1. Relay I21 uponreleasing opens conductors I20, I29, I30, I3I and I32 extending to thedistrict link and connector circuit and connects conductor I35 over itslower back contact to the winding of relay I33 so that the sender maylater operate this relay. When the marker has established connection tothe outgoing trunk 206, sender 400 then cooperates with the incomingapparatus of Fig. 3 to complete the connection to the line of the calledsubscriber 304. In connection with this incoming apparatus, aterminating sender and terminating marker (not shown in Fig. 3) areprovided. As soon as the connection to trunk 206 is established, acircuit is closed for operating relay 305 over back contacts of relay300, conductors I38 and I40 to conductors I44 and I45 extending into thesubscribers sender 400. The operation of relay 305 at first closes astart lead (not shown) that causes the terminating sender aforesaid tobe connected. After this the terminating sender receives from the sender400 the necessary information for completing in cooperation with theaforesaid terminating marker the connection to the line of the calledsubscriber 304.

After the sender 400 has completed its func tion in establishing theconnection as above outlined, it connects ground to conductor I35 tooperate relay I36 over the lowermost back contact of relay I21. Whenrelay I36 operates, it looks under control of relay I12 in a circuitfrom battery through its winding and the inner upper back contact ofrelay I12 to ground over the next to inner upper front contact of relayI36. Relay I36, in operating, closes the talking circuit to station I03.This may be traced from conductor IIO over the uppermost back contact ofrelay H2, next to uppermost front contact of relay I36, next to upperback contact of relay I12, condenser I31, lower middle front contact ofrelay I36 and outer lower back contact of relay I12 to conductor I38;also from conductor III, over the inner lower back contact of relay II2, next to inner lower front contact of relay I36, middle lower backcontact of relay I12, condenser I39, upper front contact of relay I30and upper back contact of relay I12 to conductor I40. Relay I36 alsocloses a holding circuit for relay I33, if this relay has beenpreviously operated by the marker 200 for an operator class of call, andfurnishes talking battery through the windings of relay I4I to line I00.For this purpose ground is supplied through the left winding of relayI4I, next to inner upper back contact of relay I I2 to junction pointI42 and battery is supplied through the right winding of relay I4I, nextto inner lower back contact of relay II2, to junction point I43.

After the sender 400 has completed its functions and has operated relayI36 over conductor I35 as before stated, it releases. This causescross-bar switches 40I and 402 of the sender link circuit of Fig. 4 tobe released which opens the connection to conductors H4, H5, I34, I22,I13, I44, I45 and I35. The established connection is now placed undercontrol of the district junctor circuit of Fig. 1 and is held under thecontrol of relay II1 which remains operated provided the callingsubscribers receiver is off the switchhook at station I03 and relay MIis thus maintained operated over the line loop. Relay I4I holds relay II1 operated over a circuit that may be traced from ground over the upperfront contact of relay 1, contacts of relay I4I, next to inner upperback contact of relay I12, through the winding of relay II1 to battery.

After the connection to the trunk 206 has been by the automatic releasecircuit; (g) connects ground over its next to inner lower frontv contactestablished a circuit is completed for operating the bridged impedancerelay 305 of the incoming trunk circuit over the loop extending to thecalling district junctor circuit of Fig. 1 which may be traced throughthe windings of relay 305, upper and lower back contacts of thereversing relay 306 over trunk 206, contacts of cross-bar switches 204,203, 202 and I over conductors I40 and I38, outermost back contacts ofrelay I12, upper and lower middle front contacts of relay I36, windingof polarized relay I46 and retardation coil I41 and the inner lowerfront contact of relay I I1. Relay 305 operates in this circuit, butpolarized relay I46 does not operate at this time.

When the called subscriber at station 304 answers, a circuit isestablished for operating bridged impedance relay 301 which may betraced from battery and ground through the windings thereof over the tipand ring talking conductors and contacts of cross-bar switches 300 and Iof the incoming link circuit and the cross-bar switches 302 and 303 ofthe line link circuit to the line leading to the called station 304.Relay 30'! upon operating closes an obvious circuit for reversing relay306 which, upon operating, reverses battery and ground over trunk 206thereby causing polarized relay I46 of the junctor circuit of Fig. 1 tooperate. Relay I46 upon operating connects ground to the armature ofinterrupter I through the inner upper back contact of relay I33. Whenthereafter the interrupter I48 connects ground through the lower windingof relay I23, relay I23 operates and locks to the operating groundthrough its lower inner front 1 contact. After a predetermined shortinterval, say two seconds, interrupter I48 closes a circuit foroperating charge relay I49 over a circuit from battery through thewinding of relay I49, outer lower back contacts of relays H2 and I50,offnormal contacts I69 of interrupter cam I5I upper back contact ofrelay I50, next to inner upper back contact of relay I2I upper innercontact of relay I23 through the right contact of interrupter I48 toground on its armature. Interrupter I48 1.

thus insures against the possibility of that charge relay I49 mightoperate on a momentary line closure and thereby cause the deposited coinat station I03 to be improperly collected.

Relay I49, upon operating, (a) locks under control of relay H2 in acircuit from battery through the winding of relay I49, lower backcontact of relay I I2 to ground on the lower front contact of relay I49;(b) partially prepares a path for starting an automatic release circuitto be hereinafter described by connecting the back contact of polarizedrelay I 46 over its uppermost contact to interrupter I54; (0) partiallyprepares a path for operating relay IE2 by connecting the winding ofrelay II2 over its next to inner upper contact and the lower backcontact of relay I23 to the upper contact of relay I55; (11) provides anauxiliary holding circuit for relay I36 which is required when theautomatic release circuit arrangement releases the district junctorcircuit by operating relay I12, this holding circuit extending frombattery through the winding of relay I36, lower back contact of relay I21 to ground over the upper middle contact of relay I49; (e) partiallycloses to conductor I51 to be used later by the coinpontrol circuit as asignal to collect the coin deposited in the coin box I04; and (h)closessa circuit for operating the magnet I50 to start. timing the call.This circuit may be traced from i battery through the winding of magnetI50, next to outer lower front contact of relay I l9,.inn'er upper backcontact of relay H2 to ground on: the upper front contact of relay 1. i

It is now in order to describe the operatic whereby a coin deposited incoin box I04 is col-h lected or returned or an operator is summoned tomonitor, on an overtime call or in responseto a failure of the callingsubscriber to deposit. the coin or in response to a stuck coincondition.

The collection of the deposited coin due to the disconnection of thecalling party, prior tot-he expiration of the time allowed for aconversational period will now be discussed. When the calling subscriberat station I03 disconnects, re-- lay I4I releases which in turnreleasesyrelay ill. Relay relay Ill releases. When relay II'I releases,.it causes relay I20 to operate in a circuit which may be traced fromground through the lower: winding of relay I20, upper middle frontcontact. :of relay I36, next to upper front contact of charge relay I49,lower back contact of relay I2I,

lower back contact of relay I ll, upper back con-' tact of relay I2I,next to-lower front contact of relay I36, inner upper back contact ofrelay I2I-,: to battery through resistance I59. Relay-J20 operated,looks over its inner lower front contact and the inner upper backcontact of relay; I2I to battery through resistance I59; connects groundover its lower middle front contact tothe middle lower back contact ofrelay I2! to start conductor I60 to cause a coin-control circuit to beconnected to the district junctor .circuit, and furnishes a holdingcircuit for relay I36 extending from ground over the lower frontcon-tact of relay I20, the upper back contact of relay I23 and the innerupper front c-ontactand winding of relay I36 to battery.

When ground is connected to start conductor I60 as aforesaid, the linkand control circuit of Figs. 5 to 8, inclusive, functions to cause anidle coin-control circuit SlllCh as is disclosed in Figs. 9 to 12,inclusive, to be connected to the district junctor of Fig. 1. Thedistrict junctors are divided into groups of ten, one half of whichgroups have norm-a1 access through an A group of link circuits and theother half of which groups have normal access through aB group of linkcircuits to a plurality of coin-control cir-- cuits. A link controlcircuit is provided common to the A links and a similar control circuitis provided common to the B links, each control 'circuit being providedwith ten group relays 500 to 509, inclusive, corresponding to the-tengroups of district junctors having access to t e links controlledthereby and each group of ten district junctors is provided with a groupof relays such as 600 to 603, inclusive. For the sake of clarity onlyone of the link circuits, one of the two control circuits and the grouprelays of one district junctor group have beendisclosed.

Upon the connection of ground to conductor I60, assuming that thedistrict junctor is in the tenth subgroup having normal access to a linkcircuit of the A group and assuming that there is apath available overthe. link disclosedto a I46 releases, releasing relay I23, ;when thecalled subscriber disconnects or when:

coin-control circuit, a circuit is established for the No. 9 grouprelay'509 which may be traced from conductor I60 over a back contact ofrelay 600, conductor 605, back contact of the hold magnet 103 of theprimary link switch 10!, upper back contact of relay 1'04, conductor105, back contact of relay 60I, upper back contact of relay 606,conductor 60?, winding of relay 509, individual to the calling junctorsubgroup, to battery. On calls from other junctor subgroups, similarcircuits would be extended to the windings of other group relays such as500 and 504 individual to such groups. The relays 500 to 509, inclusive,are arranged in a chain so that when simultaneous calls from dilferentsubgroups of junctors are received only that group relay is effectivewhich corresponds to the lowest numbered group of junctors in the orderof preference.

idle, and that group relay 509 is the only group relay operated, thefollowing circuits are established: (a) from ground through the windingof relay 602, upper front contact of relay 509 and upper back contactsof other group relays such as 504 and 500, conductor 5| I, No. 8 backcontact of relay 609 through resistance M to battery; (b) from batterythrough the winding of relay 606, conductor 608, to ground at the lowerfront contact of relay 500; (c) from battery through the winding ofrelay 6H, upper back contact of relay 6I2, No. 4 back contact of relay609, conductor 6| 3 to'ground at the middle lower front contact of relay509 and (d) at its upper back contact opens the circuit of relay 5I0which releases to apply ground to conductor M2 for starting a timingoperation. With relay 602 operated, a locking circuit is established forrelay 509 which may be traced from battery through its winding and innerlower front contact, conductor 5l3, lower front contacts of relay 602,conductor 5| 4, inner upper front contact of relay 509 and over theinner upper back contacts of other relays such as 504 and 500 to round.

Relay 606 upon operating opens the operating circuits of relays 500-509,and with relay 602 operated as described, closes a circuit for operatingrelay 600, extending from ground over its next to lower front contact,the inner upper front contact of relay 602 to battery through thewinding of relay 600. Relay 600, upon operating operates relay 603 in acircuit from battery through its winding, the upperfront contact ofrelay 602 to ground at the front contact of relay 600 and individualizesthe start conductors such as I60 of the subgroup of junctors in whichthe calling junctor is located so that they become available foridentifying the junctor which is calling. With relay 603 operated, thestart conductors from the calling subgroup of junctors are extended tothe operating windings of relays H0 to H9, inclusive and assuming thatthe district junctor of Fig. 1 is the first junctor of the subgroup, acircuit is effective for operating relay H0 extending from groundapplied to the start conductor I60, No. 3 contact of relay 603, No. backcontact of relay 6M, conductor 6I5, upper winding of relay H0 tobattery. If there is more than one simultaneous call in the subgroup oneor more of relays H0 to H9, inclusive, may 0perate. The operation of anyone of these relays establishes a circuit for relay 6I2 extending frombattery through the winding of relay BIZ, upper front contact of relay6| I, conductor 6H5, lower It being assumed that both control circuitsare front contacts of operated relays H0 to H9, inclusive, conductor 6",No. 6 back contact of relay 609, No. 2 front contact of relay 603,conductor 605, thence as traced to conductor I05, lower front contact ofrelay 002, conductor 5M, inner upper front contact of relay 509, andover the inner upper back contacts of other group relays includingrelays 505 and 500 to ground. Relay 6l2 locks over its upper frontcontact to the operating circuit just traced independent of relay 6| I;at its upper back contact opens the operating circuit of relay 6H whichstarts to release and at its inner lower front contact prepares alocking circuit for an operated relay of the groups H0 to H9, inclusive,and an operating circuit for relay 6M as later described.

With the link circuit disclosed idle, as assumed, relay 593 uponoperating establishes a circuit from ground over the lower back contactof hold magnet I06 of the primary link switch l'fll, conductor 50?, No.14 contact of relay 603, conductor 646, lower back contact of relay 5I5,winding of relay 5| 6 to battery. If relay 002 is not operated,indicating that the first group of five coin-control circuits in whichthe control circuit disclosed in Figs. 9 to 12, inclusive, is located,is not being held by another link and control circuit and two or morecoincontrol circuits of the group are idle, a circuit will beestablished upon the operation of relay 5l6 extending from batterythrough the upper winding of relay 823, conductor 808, lower backcontact of relay T04, conductor I08, contact of relay 5I6, lower backcontact of relay 5I'l, conductor sat; next to lower back contact ofrelay 802, upper back contact of relay 89I and to ground over chaincontacts controlled by the coin-control circuit busy relays 805 to 801,inclusive of the group. Similar test circuits are established by theoperation of relay 5I6 or of relay 5I9 to determine if there are two ormore idle coin-control circuits in the three other groups to which thelink circuits have access and if such idle control circuits are found,the corresponding coin-control circuit group relays 824 to 326 will alsobe operated.

It will be recalled that upon the operation of relay 6I2,slow-to-release relay 6II started to release. As soon as relay 6 isfully released and closes its back contact, a circuit is thereuponestablished for relay 5H extending from battery through the winding ofrelay 5I1, conductor 520, back contact of relay GM to ground at theinner upper front contact of relay 6l2. If any group of coin-controlcircuits is not being held busy by another link and control circuit orif the coin-control group busy relay 86! is not operated, thecorresponding group relays 823 to 026 will be operated. For example, therelay 623 will be operated in a circuit from battery through its upperwinding, thence as traced over the front contact of relay 516, middlelower front contact of relay 5I'I, conductor 52I, outer lower backcontact of relay 802 to ground at the inner upper back contact of relayL When one or more of the group relays 023 to 826, inclusive, haveoperated on either the first or second test, a circuit is closed foroperating one of relays 609 to 8H individual respectively to the severallink and control circuits. In the present instance relay 809 will beoperated in a circuit extending from ground through its winding, lowerfront contact of group relay 823, conductor BIZ, No. 1 front contact ofrelay 603, lower front contact of relay 6I2, No. 9 back contact

